Can't figure out how to get target framework version of a package via NuGet API?

My first thought was it's a pretty simple question - turned out that it's not. Or I missed something.
For a little bit of tooling I'm writing, I need to figure out target framework version (3.5, 4.0, etc.) of a package, given it's id and version. So far, no success. I referenced NuGet executable to get access to the API, and I assume NuGet.Core package does
pretty much the same thing.
My understanding was that it should be hidden somewhere behind IPackageMetadata interface, but I couldn't find it so far.
I tried:

IPackageMetadata.FrameworkAssemblies - seems to always be an empty array;

PackageDependencySet.TargetFramework and SupportedFramework properties - same result, "Enumeration yielded no results".
So, is there a way to do it via API? If there isn't one, I'd be happy to do a pull request if someone can point me in the right direction.
P.S. Having TargetFrameworkProfile (e.g. Full, Client) would also be nice.

Great. So, to get info on 10 packages I need to download all the binaries (it will take time and traffic even with the fast network) and then do a directory search, mapping directories to framework versions.
What's even worse - every developer that want to do that in the future will search for the solution and then likely do the exact same thing. Even if I create NuGet package that does this, it won't do the justice.
I love Microsoft.
Thanks for clarification @ferventcoder - my above words shouldn't concern you. I'm just thinking out loud.

But VS extension definitely has this information - if you want to install a package version that depends on 4.0 in a 3.5 project, you'll get an error.
So what is it - someone forgot to put it into API? That's private info, may be.